Motor control.



W. I. SLIOHTER.

MOTOR CONTROL.

APPLICATION 31mm JUNE 23, 1909.

973,575. Patented 0ct.25,1910.

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NEW YORK, ASSIGNQR TRIS COMPANY, A CORPORATKON GE NEVJ YQRK.

,M'QTGE CONTROL.

Application filed June To all whom it may concern:

Be it known that l, WALTER Smonrnn, a citizen of the United States, residing at Schenectady, county Schenectady, State of New York, have invented certain new and useful Improvements in Motor Control, of which the following is a specification.

My invention relates to the control of a plurality of electric motors mechanically connected to drive a common load as, for instance, the control of a plurality of modriring an electric car or locomotive.

The object of my invention is to provide a simple method of control and arrangement of apparatus adapted therefor whereby the motors may he started and accelerated without at any time opening the circuit of all the motors.

In carryingout my invention 1 connect the motors electrically in a plurality of groups and my method 01"; control consists in starting the motors by impressing reduced voltages on the groups, and increasing the voltages oi the groups alternately. While the circuit connections of one group are being varied to increase the impressed voltage group, the circuit connections of the other group or groups are maintained, so that all the motors are never open circuited. My irwention is particularly advantageous in its application t alternating current mo tors, since the nsf oruier winding from which the motors are supplied 'torins coir supplying voltages to the several motor groups independently. The motors may, for instancc, be connected all in series points on the transformer winding, and a connection made from the middle point of the motor circuit to an intermediate point on the transformer winding so as to divide the motors into two groups on which independent voltages are impressed from' the transformer; then, by shifting the terminal connections alternately with respect to the intermediate point of 1c t'ansfornier winding, the voltages on the two groups of motors are alternately increased, the circuit of each group being maintained while the ci cuit connections of the other are being varied.

My invention will best be understood by reference to the accompanying drawing which shows diagrammatically a motor control system arranged in accordance with my invention.

Specification of Letters Patent.

es, 15cc; semi cult are thus alternately shifted middle point of theinotor circuit, that is,

the junction hetween motors and connected to the center or" the secone winding of the transformer ll, so as vide the motors into two groups, one consist- 'ing of motors A A the other or motors This intermedia 1 connection may he grounded, as indicated in the drawing, in orderto keep the insulat tion strains between the motor windings the frames down to an amount not exceeding half the secondary voltage of the trans-- former B. I

When the switch C is moved to position, indicated by dotted line its 1, contactors D and D are energized and connect,

the terminals of the motor circuit to the w n points on the secondary or the transrormer B nearest to the central point. As the switch (3 is moved from itsfirst to its sec-,

end position, contactor de'clnergize" and contacto-r D is then energized, so as to shift one terminal of the motor circuit farther away from the central point on the transformer. While the circuit of motors A and A is momentarily opened during this change in connections, the circuit of motors A and A is kept closed. in movin from its second to its third position, contactor D remains energized but contactor D is cleenerg'ized and contactor l3 energized. 'lhus the other termina of the motor circuit is shifted farther a' y from the central point on the transformer. the switch C is moved through its other sitions the terminals of the motor cirso as to increase the voltage impressed on the two groups of motors step-by-step and alternately and at no time are more than half the motors open circuited. Furthermore, since while the motors are operating, independent voltages are impressed on each group, slipping of the wheels driven by one niotor or group of motors cannot robthe motors of the other group of voltage as would.

h int-J be the case if the motors were all in series in a single group.

I do not desire to limit myself to the particular arrangement and connect-ions shown and described, but aim in the appended claimsto cover all modifications which are within the scope of my invention..

What I claim as new and desire to se-' cure by Letters Patent of the United States, is

of electric motors mechanically connected to drive a common load, and connected electrically in a plurality of groups, which consists in starting the motors by impressing reduced voltages on the groups, and increasing the voltages on said groups alternately. U

2. The} method of operating a plurality of electric motors mechanically connected to drive a common load, and connected electrically in a plurality of groups, which consists in starting the motors by impressing reduced voltages on the groups, and increasing. the voltages on said groups alternately stepby-step, the voltage being maintained on one group while the voltage on another group is being increased.

3. The method of operating a plurality of electric motors mechanically connected. to drive a common load, and connected electrically in a plurality of groups, which consists in so connecting the groups to the source that voltages are impressed on the groups independently, and varying the connections of said groups alternately to increase the impressed voltages.

4. The method of operating a plurality of electric motors mechanically connected to drive a common load, and connected electrically in a plurality of groups, which consists in so connecting the groups to the source that voltages are impressed on the groups independently, and varying the'connections of said groups alternately to. increase the impressed voltages step-by-step,

the connections of one group being main-- taincd While the connections of another group are being varied.

5. In combination, a plurality of electric motors mechanically connected to drive a common load and electrically connected in a plurality ot'lgroups, means for impressing voltages on said groups independently, and a controlling switch adapted to vary the voltage on the several groups alternately.

6. In combin ion, a, plurality of electric motors mechanically connected to drive a common load and electrically connected in a plurality of groups, means for impressing T1. The method of operating a plurality volt-ages on said groups independently, and

controlling switch adapted to vary the connections of said groups alternately to increase their impressed voltages step-by-step and to maintain the connections of one group while varying those of another.

7. In combination, a plurality of electric motors mechanically connected to drive a common load and electrically connected in a plurality of groups, a source of independ ent voltages for the several groups, and-a controlling switch adapted to connect the several groups to the source and to vary the connections of said groups alternately to increase the impressed voltages step-by-step.

8. In combination, a plurality 01 electric motors mechanically connected to drive a common load and electrically connected in a plurality of groups, a source of independent voltages for the several groups, and a controlling switch adapted to connect the several groups to the source, in moving to a subsequent position to vary the connections of one group to increase its impressed voltage while maintaining the connections of a second group, and in moving to a still subsequentposition to vary the connections of the second group to increase its impressed voltage while maintaining the connections of the first group.

9. In combination, a plurality of alternating current motors mechanically connected to drive a common load and electrically con nected in a plurality of groups, a transformer winding for supplying current to said motors, and a switch adapted to connect said groups independently to said winding and to vary alternately rhs connections of said groups to said winding, maintaining the connections of one group While varying that of another. 1 t

10. In combination, a plurality of alternating current motors mechanically connect ed to drive a common load and electrically connected in series, a transformer winding for supplying current to said motors, connections from the terminals of the motor circuit to points on the transformer, a connection from an intermediate point of the motor circuit to an intermediate point on the transformer, and a controlling switch adapted to shift the terminal connections alternately with respect to said intermediate point on said winding.

In witness whereof, I have hereunto'set my hand this 22nd day of June, 1909.

\VALTER I. SLICHTER.

Witnesses:

BENJAMIN B. HULL, HELEN Onronn. 

